Roy,

Well the intuition was correct, however the problem is one level more complex.
The Smith chart shows the following approximate 'mirror' relationships for j=0:

Load Input Measurement
20 125
25 100
35 71
10 250
50 50

It is a "log" mirror centered on 50 Ohms. The mirror relationship holds for j /=
0, however the calculation is more complex. - Dan

Roy Lewallen wrote:
dansawyeror wrote:

The program zl_zin calculates a Zload from a known Zin. It would seem
that given a symmetrical feedline that Zin and Zload should be
mirrors. Why is that not so?


I'm not sure what you mean by "mirrors". But the relationship between
Zin and Zload is dictated by the way transmission lines transform
impedances. A better question is, why should it be anything else?

A series inductor is symmetrical, is it not? Suppose you have a series
inductor with impedance +j10 ohms in a box. Connect it to a load of 50 +
j0 ohms. Looking into the input of the series inductor, you see 50 + j10
ohms. Now put a load of 50 + j10 ohms at the output instead of 50 + j0.
Are you saying you expect to see 50 + j0 at the input? Why?

Is there a program that will calculate Zin from a known Zload?


Hopefully someone else will be able to answer that.

Roy Lewallen, W7EL